How to check if an extention is installed

问题

We offer multiple iMessage extensions. Example ExtensionA and ExtensionB.

ExtensionB offers InApp purchases InAppPurchaseA and InAppPurchaseB.

InAppPurchaseA should be free, if ExtensionA is installed on the device.

How to check if ExtensionA is installed?

来源：https://stackoverflow.com/questions/40574375/how-to-check-if-an-extention-is-installed